Gyroscope motion, such as motion from a resonator, may be detected by amplifying small currents generated from the motion using electrical amplifiers. However, measuring these currents is difficult, because the electrical components may have a significant amount of parasitic capacitance and the amplifiers may generate additional noise.
Optical vibrometer measurements completely eliminate interaction with stray capacitances and the magnitude of the signal depends only on the strength of a laser sources, and not on the magnitude of the motion.
Vibratory micro scale gyroscopes are often tested in the lab using table-top laser vibrometers, as described by C. Acar, A. Shkel in MEMS Vibratory Gyroscopes, Spring 2009, and U.S. Pat. No. 5,883,715, issued Mar. 16, 1999, incorporated herein by reference.
The principle of operation of a laser Doppler vibrometer, as described by G. A. Massey in “An Optical Heterodyne Ultrasonic Image Converter” PROCEEDINGS OF THE IEEE, VOL. 56. NO. 12, DECEMBER 1968, incorporated herein by reference, has been developed and explored extensively in the literature.
Recently, there has been interest in lower cost, portable laser vibrometers for bio-medical applications. Such chip-scale laser vibrometers are described by Yanlu Li, Patrick Segers, Joris Dirckx, and Roel Baets in “On-chip laser Doppler vibrometer for arterial pulse wave velocity measurement”, Biomedical Optics Express, Vol. 4, Issue 7, pp. 1229-1235 (2013), and by Yanlu Li and Roel Baets in “Homodyne laser Doppler vibrometer on silicon-on-insulator with integrated 90 degree optical hybrids”, Optics Express, Vol. 21, Issue 11, pp. 13342-13350 (2013), which are incorporated herein by reference.
The prior art approaches require relatively large volumes and are not suitable to meet very small form factor requirements. They also have performance issues caused by stray reflections.
What is needed is a gyroscope that is very stable, that has a very small form factor, and that can be used in applications where cost, size, weight, and power are at a premium. The embodiments of the present disclosure answer these and other needs.